Engine 1994 GT under drive pulley

I never had issues with cooling or charging with my sn95. Underdrive everything with a 180* t stat and a 3 core radiator kept everything nice and cool. This was in 95 deg weather.

The 94/95 mustangs have 130 amp alternators too. I doubt you’ll notice much of a difference in charging.

Well, congratulations? I'm not typically one to hinder someone's joy, but... can't really let this feedback stand for others to come across.

You managed to find a 95 degree day to get stuck in traffic and sit at idle in the middle of summer so you're positive your cooling system wasn't impacted? Dude, it's winter. Even in sunny California you're in the 60's. No one said it would blow up your car, only that it would negatively impact your cooling at peak conditions - when you really need it, which it did if you've now seen 'better performance.'

You also managed to run it at night, stuck in a similar traffic jam, with headlights, radio, and A/C or heater running and didn't see your headlights dim? Seriously, I've had the belt completely off to move the car around in the shop and couldn't brag about such gains. Perhaps those pulleys were made of forged magical fairy dust too? Again, it wasn't going to destroy your alternator, just cut down its peak performance - when you really need it.

You gotta love how these snake-oil mods are always 'proven' by the butt dyno. Smoother, better burnouts, feels stronger my girlfriend swears it does. And unless you do a dyno pull, and immediately swap out the pulleys, and then another run with no other changes, your results (current and previous) are unscientific at best. You do realize a 60 degree day vs a 90 degree day at the dyno is worth over 20hp right? My turbo 5.0 is noticeably more powerful on cool days - so much so that I had to upgrade the ignition system against spark blowout. And even the slightest calibration difference between dynos or days at the dyno is more than that?

On a good day, on an SN95 5.0, which doesn't rev all that high unlike the 4-7hp numbers you've seen posted about Coyotes that go to 7k+, you got 4hp. That's with all the pulleys swapped not just the one. Nothing you can truly feel, it's 100x more likely that it was a nice day outside. I've had my SN95 for almost 25 years, so I've tried pretty much everything. The underdrive pulleys did almost nothing, but made me overheat in traffic. Those cat-backs made the car sound nice, but it still did nothing. And when I finally realized I'd wasted a lot of $ and my car was still whipped by the Camaros and New Edge Mustangs at the time, I decided it was Forced Induction, a stroker kit, or a nice HCI that would solve that problem.

Again, congratulations, if it makes you happy more power to you - at least it was free. But posting for others who come across this, underdrive pulleys are still snake-oil. They have some slight merit, but they do compromise your accessories when you need them, and there are loads of better ways to make much more power. Your exaggerated claims about their effect kind of prove the earlier point - it's wishful thinking. Your car is no more powerful, and your schlong didn't grow an extra 3" either. Snake oil salesman stay in business and have repeat customers because of the placebo effect, and cognitive dissonance - it MUST be faster because I put this time / $ into it.

Finally, congratulations. But the next person who asks, they'll get the same answer around here.